Molten metal feed nozzle

ABSTRACT

A nozzle end is provided with an extension  11  which has a lower portion immersed in a molten metal pool and extends toward a side weir  2  such that a stagnation area disappears on a free liquid surface of molten metal. 
     The extension  11  is in the form of a quadrangular pyramid lying sidelong and is converged to a point P 1  extremely close to the side weir  2.    
     According to this molten metal feed nozzle, a stagnation area on a free liquid surface of molten metal is displaced by the extension  11  contiguous with the nozzle end to suppress generation of an unwanted solidification shell. Thus, no unwanted solidification shell is pinched as foreign matter by solidification shells generated on outer peripheries of chilled rolls  1  for production of a strip and break of a strip derived from enlargement of nip between the rolls can be averted.

TECHNICAL FIELD

The present invention relates to a molten metal feed nozzle incorporatedin a twin roll caster

BACKGROUND ART

FIG. 1 shows an example of a twin roll caster with a pair of chilledrolls 1 arranged horizontally and in parallel with each other and a pairof side weirs 2 associated with the chilled rolls 1.

The rolls 1 through which cooling water flows interiorly are adapted toincrease or decrease a nip or gap G between the rolls depending uponthickness of a strip 3 to be produced

Rotational directions and velocities of the rolls 1 are set such thatrespective outer peripheries of the rolls are moved from above towardthe nip G at constant velocity.

One and the other of the side weirs 2 are urged to surface-contact oneand the other ends of the rolls 1, respectively. In a space surroundedand defined by the side weirs 2 and rolls 1, a molten metal feed nozzlemade of refractory is positioned just above the nip P between the rolls.

The feed nozzle has an elongated nozzle trough 5 which in turn has a topopened for reception of molten metal 4 and longitudinal side wallsformed at their lower ends with a plurality of openings 6 for passagefrom the trough 5 to the outer peripheries of the rolls 1, the openingsbeing spaced apart from each other axially of the rolls. By pouring themolten metal 4 into the nozzle trough 5, a molten metal pool 7 is formedabove the nip G between the rolls and in contact with the outerperipheries of the rolls 1.

More specifically, when the molten metal pool 7 is formed and the rollsl chilled by passage of the cooling water are rotated, the molten metal4 is solidified on the outer peripheries of the rolls 1 and the strip 3is delivered downwardly from the nip G between the rolls.

Since wear on sliding portions of the side weirs relative to the rolls 1progresses in direct proportion to accumulative operational time period,force for urging the side weirs 2 against the rolls 1 is graduallyincreased to prevent leakage of the molten metal 4 from between suchmembers.

Molten metal feed nozzles incorporated in twin roll casters may bedivided into those with ends of the nozzle which surface-contact theside weirs 2 (see, for example, Reference 1) and those with ends of thenozzle which are spaced apart from and in parallel with the side weirs 2sees for example, Reference 2).

[Reference 1] JP 62-45456A [Reference 2] JP 6-114505A SUMMARY OF THEINVENTION Problems to be Solved by the Invention

However, in application of a structure in Reference 1, the molten metalfeed nozzle remains unchanged in its longitudinal size. Thus, as thewear on the sliding portion of the side weir 2 progresses, leakage ofthe molten metal 4 becomes unsuppressed by merely increasing the forcefor urging the side weirs 2 to the rolls 1.

In application of a structure in Reference 2, as shown in FIG. 10, flowvelocity distribution at free liquid surface of the molten metal 4 tendsto be low at between two parallel surfaces facing to each other i.e., asurface 9 of the side weir on the molten metal pool and an end wallsurface 10 of the molten metal nozzle, in comparison with at between alongitudinal side wall surface 8 of the molten metal nozzle and thechilled roll 1. As a result, an area A where the molten metal 4 tends tostagnate is formed especially from the end wall surface 10 to a point P0which is an intersection of nip center line L with the surface 9 of theside weir.

It occurs in the stagnation area A that the molten metal 4 is lowered intemperature due to radiation heat transmission and a solidificationshell is generated which is unwanted for the free liquid surface of themolten metal 4 and for the end wall surface 10 of the nozzle.

When such unwanted solidification shell is pinched as foreign matter bythe solidification shells generated on the outer peripheries of thechilled rolls 1 upon rotation of the rolls, the strip 3 may be locallythickened into defective shape and/or the nip G between the rolls may beenlarged depending upon part of the strip 3 where the foreign matter ispinched, resulting in break of the strip 3 due to reduction in coolingefficiency and heat recuperation from the molten metal 4.

The invention was made in view of the above and has its object toprovide a molten metal feed nozzle which can avert break of a strip

Means or Measures for Solving the Problems

In order to attain the above object, the invention is directed to amolten metal feed nozzle positioned above a nip between rolls of a twinroll caster and having ends spaced apart from side weirs comprisingextensions each contiguous with the nozzle end and extending toward theside weir such that a stagnation area disappears on a free liquidsurface of molten metal.

In the invention, the extensions eliminate stagnation areas of the freeliquid surface of the molten metal; they prevent the molten metal frombeing lowered in temperature due to radiation heat transmission andsuppress generation of unwanted solidification shells.

EFFECTS OF THE INVENTION

According to a molten metal feed nozzle of the invention, the followingexcellent effects and advantages can be obtained.

(1) The extensions prevent the molten metal adjacent to the side weirsfrom being lowered in temperature and suppress generation ofsolidification shells on the free liquid surface of the molten metal, sothat unwanted solidification shells are not pinched as foreign matter bythe solidification shells generated on the outer peripheries of thechilled roll for production of the strip, and thus break of the stripderived from enlargement of the nip between the rolls can be averted.

(2) When the extensions are shaped to be converged toward the side weirsfor gradual reduction in volume of the extensions, heat transmissionfrom the molten metal to the extensions is reduced so that the moltenmetal adjacent to the side weirs is effectively prevented from beinglowered in temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] A schematic diagram showing an example of a twin roll caster.

[FIG. 2] A schematic diagram showing flow velocity distribution on afree surface of molten metal adjacent to a molten metal feed nozzleshown in FIG. 1.

[FIG. 3] A partial perspective view from below showing a firstembodiment of a molten metal feed nozzle according to the invention.

[FIG. 4] A schematic diagram of the molten metal feed nozzle in FIG. 3looking axially of the chilled rolls.

[FIG. 5] A schematic diagram of the molten metal feed nozzle in FIG. 3looking tangentially of the chilled roil.

[FIG. 6] A schematic diagram showing flow velocity distribution on afree surface of molten metal adjacent to the molten metal feed nozzle ofFIG. 3.

[FIG. 7] A partial perspective view from below showing a secondembodiment of a molten metal feed nozzle according to the invention.

[FIG. 8] A schematic diagram of the molten metal feed nozzle in FIG. 7looking axially of the chilled rolls.

[FIG. 9] A partial perspective view from below showing a thirdembodiment of a molten metal feed nozzle according to the invention.

[FIG. 10] A schematic diagram of the molten metal feed nozzle in FIG. 9looking axially of the chilled rolls.

EXPLANATION OF THE REFERENCE NUMERALS

2 side weir

7 molten metal pool

11,12,13 extension

A area

G nip or gap

P1 point

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be described in conjunction with thedrawings.

FIGS. 3 to 6 show a first embodiment of a molten metal feed nozzleaccording to the invention in which parts identical with those in FIGS.1 and 2 are represented by the same reference numerals.

Each of nozzle ends is provided with an extension 11 which has a lowerportion immersed in a molten metal pool 7 and extends toward a side weir2 such that a stagnation area A (see FIG. 2) disappears on a free liquidsurface of molten metal 4.

The extension 11 is in the form of a quadrangular pyramid lying sidelongand is convergent to point P1 extremely close to the side weir 2.

In the twin roll caster with such molten metal feed nozzle incorporated,the stagnation area A on the free liquid surface of the molten metal 4is displaced by the extension 11 contiguous with the nozzle end tosuppress generation of an unwanted solidification shell. As a result, nounwanted solidification shell is pinched as foreign matter by thesolidification shells generated on the outer peripheries on the chilledrolls 1 for production of the strip 3, whereby break of the strip 3 dueto enlargement of the nip G between the rolls can be averted.

In addition, the extension 11 is gradually reduced in volume toward theside weir 2, so that heat transmission from the molten metal 4 to theextension 11 is reduced. As a result, the molten metal 4 adjacent to theside weir 2 can be effectively prevented from being lowered intemperature and no unwanted solidification shell for the side weir 2 isgenerated.

FIGS. 7 and 8 shows a second embodiment of a molten metal feed nozzleaccording to the invention. In the figures, parts identical with thoseshown in FIGS. 3 to 6 are represented by the same reference numerals.

Each of nozzle ends is provided with an extension 12 which has a lowerportion immersed in a molten metal pool 7 and extends toward a side weir2 such that a stagnation area A (see FIG. 2) disappears on a free liquidsurface of molten metal 4.

The extension 12 is wedge shaped and is converged to a horizontal linesegment between points P2 and 23 extremely close to the side weir 2.

In the twin roll caster with such molten metal feed nozzle incorporatedthe stagnation area A on the free liquid surface of the molten metal 4is displaced by the extension 12 contiguous with the nozzle end tosuppress generation of unwanted solidification shell. As a result, nounwanted solidification shell is pinched as foreign matter by thesolidification shells generated on the outer peripheries of the chilledroll 1 for production of the strip 3, whereby break of the strip 3 dueto enlargement of the nip G between the rolls can be averted.

In addition, the extension 12 is gradually reduced in volume toward theside weir 2, so that heat transmission from the molten metal 4 (see FIG.6) to the extension 12 is reduced so that the molten metal 4 adjacent tothe side weir 2 can be effectively prevented from being lowered intemperature and no unwanted solidification shell for the side weir 2 isgenerated.

FIGS. 9 and 10 show a third embodiment of a molten metal feed nozzleaccording to the invention. In the figures, parts identical with thosein FIGS. 3 to 7 are represented by the same reference numerals.

Each of nozzle ends is provided with an extension 13 which has a lowerportion immersed in a molten metal pool 7 and extends to a side weir 2such that a stagnation area A (see FIG. 2) disappears on a free liquidsurface of molten metal 4.

The extension 13 is in the form of tapered quadratic prism lyingsidelong and is converged to vertical face with corners P2, P3, P4 andP5 extremely close to the side weir 2.

In the twin roll caser with such molten metal feed nozzle incorporated,the stagnation area A of the free liquid surface of the molten metal 4is displaced by the extension 13 contiguous with the nozzle end tosuppress generation of unwanted solidification shell. As a result, nounwanted solidification shell is pinched as foreign matter by thesolidification shells generated on the outer peripheries of the chilledroll 1 for production of the strip 3, whereby break of the strip 3derived from enlargement of the nip G between the rolls can be averted.

Heat transmission from the molten metal 4 (see FIG. 6) to the extension13 may be much in comparison with the first and second embodiments;however, the third embodiment is easier in machining upon fabrication ofthe molten metal feed nozzle.

It is to be understood that a molten metal feed nozzle of the inventionis not limited to the above embodiments and that various changes andmodifications may be made without departing from the scope of theinvention.

INDUSTRIAL APPLICABILITY

A molten metal feed nozzle of the invention is applicable to productionof strips of steel or other various metals.

1. A molten metal feed nozzle positioned above a nip between rolls of atwin roll caster and having ends spaced apart from side weirs,comprising extensions each contiguous with the nozzle end and extendingtoward the side weir such that a stagnation area disappears on a freeliquid surface of molten metal.
 2. A molten metal feed nozzle as claimedin claim 1, wherein the extension is converged toward the side weir. 3.A molten metal feed nozzle as claimed in claim 1, wherein the extensionis converged to a point extremely close to the side weir.